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Stephanie C. Goodhew, Hannah L. Boal, Mark Edwards; A magnocellular contribution to conscious object perception via temporal object segmentation . Journal of Vision 2014;14(10):1334. doi: https://doi.org/10.1167/14.10.1334.
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© ARVO (1962-2015); The Authors (2016-present)
The human visual system is continuously confronted with dynamic input. One problem that the system must solve, therefore, is recognising when two distinct objects have appeared at a given location despite their brief presentation and rapid succession (temporal object segmentation). Given the superior temporal sensitivity and faster conduction speeds of magnocellular neurons relative to parvocellular neurons, here we examined the role of magnocellular neurons in temporal object segmentation. We measured temporal object segmentation via object substitution masking (OSM), which reflects the failure to distinguish the target and mask as distinct objects through time (see Goodhew et al., 2013, PBR, for a review). Specifically, participants' task was to identify the location of the gap in a target Landolt C surrounded by four-dots when the target and four-dots disappeared simultaneously (simultaneous mask offset, unmasked control) or when the four-dots temporally-trailed after target offset (delayed mask offset, masked condition). We isolated the selective role of magnocellular neurons by comparing target identification performance under conditions of pulsed versus steady luminance pedestals. A pulsed pedestal is designed to saturate the magnocellular response with a rapid pulse of luminance concurrent with the target array, whereas a steady-pedestal condition leaves both the magnocellular and parvocellular channels available to process the target (Pokorny, 2011, JOV). Across two experiments, we found that OSM magnitude was selectively enhanced under pulsed pedestal conditions, despite the fact that the pulsed pedestal did not alter overall target identification accuracy. This indicates that magnocellular neurons underlie our ability to resolve and consciously perceive two distinct objects despite their close spatiotemporal proximity. Given that this process of temporal object segmentation has consequences for which stimuli are consciously perceived, this demonstrates a functional role via which magnocellular neurons contribute to determining the contents conscious perception.
Meeting abstract presented at VSS 2014
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